孤岛模式下串联型微电网逆变系统动态建模

Dynamic Modeling of Inverter System in Isolated Series Micro-grids

针对目前H桥逆变单元串联系统中传统线性控制器设计缺乏数学模型支持,闭环控制作用下系统稳定性也难以进行分析的问题,以孤岛模式下3单元串联型微电网为研究对象,建立了逆变系统的动态模型。首先介绍了串联型微电网的拓扑结构与逆变系统的等效模型;其次建立了逆变系统的状态空间平均模型与小信号模型,并给出了相应的等效电路模型及主要传递函数;最后基于MATLAB/SIMULINK软件环境及串联型微电网模拟实验平台进行了串联逆变系统动态行为分析。结果表明:直流侧他控型电流源输出及控制输入变化量与所引起的输出电压变化量之间呈线性关系,且仍满足各单元相互叠加的关系;仿真运行模型、实验电路输出的动态特性均与理论分析结果相一致,由此表明了所建模型的正确性。

The design for conventional linear controller of series inverter system with H-bridge inverter units lacks the support of mathematical model, and it is difficult to analyze its system stability under closed-loop control condition. Thus we established a dynamic model of inverter system based on a micro-grid of three units connected in series. Firstly, we introduced the topology of series micro-grids, as well as the equivalent model of the inverter system. Secondly, we established a state space average model and a small signal model of the inverter system, and obtained their corresponding equivalent circuit model and transfer functions. Finally, we analyzed the dynamic behavior of the inverter system through simulation in MATLAB/SIMULINK and experiments on a micro-grid experiment platform. The simulation results show that the variation of a non-automatic current source＇s output and the controller＇s input is linear to the variation of the output voltage, while maintaining the mutual superposition among the units. The output dynamic characteristics of the simulated model and the experimental system are consistent with those from the theoretical analysis, verifying the feasibility of the proposed model.